STEYX Function in Excel: Typical Error of a Trend Line

STEYX Function in Excel: Typical Error of a Trend Line featured illustration

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⏱ 2 min readUpdated 5 October 2026

StatisticsLevel: ExpertAvailable in: Excel 2007+

In this article
  1. Syntax
  2. Examples
  3. Example 1
  4. STEYX in practice
  5. Where you will use it
  6. Worked example
  7. Mistakes people make
  8. Related functions
  9. Continue learning

STEYX returns the standard error of predicted y values — roughly how far actual points sit from the trend line.

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Syntax

=STEYX(known_ys, known_xs)
Argument What it means
known_xs Same length as known_ys.

Examples

Example 1

=FORECAST.LINEAR(A26, C2:C25, A2:A25) + {-2, 2} * STEYX(C2:C25, A2:A25)

A rough low/high band around a forecast.

STEYX in practice

Where you will use it

  • Typical error of a trend prediction
  • Forecast accuracy
  • Regression quality

Worked example

CaseFormulaResult
1=ROUND(STEYX(INDEX($H$1:$L$3,A2,0),{1,2,3,4,5}),4)0
2=ROUND(STEYX(INDEX($H$1:$L$3,A3,0),{1,2,3,4,5}),4)0.5164
3=ROUND(STEYX(INDEX($H$1:$L$3,A4,0),{1,2,3,4,5}),4)12.7802

Results calculated in Excel.

Mistakes people make

MistakeWhat to do instead
Fewer than 3 points#DIV/0!
UnitsSame units as y

RSQ · FORECAST.LINEAR

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